EFFECT name=COLLECTION (var-list </ DETAILS>);
You use a collection effect to define a set of variables that are treated as a single effect with multiple degrees of freedom. The variables in var-list can be continuous or classification variables. The columns in the design matrix that are contributed by a collection effect are the design columns of its constituent variables in the order in which they appear in the definition of the collection effect. If you specify the DETAILS option, then a table that shows the constituents of the collection effect is displayed.